ISSUE-225: Define normalization for matching CSS identifiers

Define normalization for matching CSS identifiers

For CSS identifiers that are CSS-internal (@namespace prefixes, counter names, etc.), we need to define how normalization is applied.
- Are they normalized before matching (i.e. decomposed and composed forms
are considered to represent the same thing)
- Are they not normalized before matching (i.e. decomposed and composed forms
are considered to represent different things)

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Created issue 'Define normalization for matching CSS identifiers' nickname owned by Elika Etemad on product CSS4 Values and Units, description 'For CSS identifiers that are CSS-internal (@namespace prefixes, counter names, etc.), we need to define how normalization is applied.
- Are they normalized before matching (i.e. decomposed and composed forms
are considered to represent the same thing)
- Are they not normalized before matching (i.e. decomposed and composed forms
are considered to represent different things)
' non-public